Metropolitan Haze?

[AEAJR (Ed)]

I live on Long Island, about 25 air miles East of Manhattan, NYC. I think I am living on the edge of the haze that hangs over the NYC area.

It seems that no matter how clear the sky appears, no matter how good the seeing is, bright objects like Jupiter, Mars and Venus always have a kind of a glow around them and I get a cross pattern in the eyepiece. In my 38 and 25 mm eyepieces, under 50X, where the moon does not fill the view I get some of this but it is not as noticeable and it does not show up in the few camera phone pictures I have taken.

At first I thought it was my eyes, but new glasses have not eliminated the glow and the cross. Feels like here is dirt on the lens but I don't think that is the case.

It is consistent across all eyepieces and in both of my scopes. So I am presuming this is not an anomaly of the optics or a collimation thing.

I have tried various filters but they do not eliminate the issue.

It is not as noticeable when looking at stars or clusters, but it is still there.

Should I assume that I am just looking through a less than transparent atmosphere even when the sky looks clear?



How about you other city and close suburb folks? Do you see this too?

Any advice on how to minimize this effect?

[Nikolas (Nik)]

You haven't lived in Melbourne then if you think you have atmospheric issues....

[AEAJR (Ed)]

I see. so it isn't just me.

[ZeroID (Brent)]

Nup, pretty normal for CBD viewing.
I get good nights when a cold clear southerly comes up from the Antarctic and blows all the crud away. Nor'easters from the tropics are full of moisture and dust from Australia.
And of course the general city 'fug' from cars etc which hangs over the 'burbs.

[Nikolas (Nik)]

Yep defintely the best conditions always follow a southerly blast.

[Wavytone]

Melbourne ? LOL...

Try some of the big cities in China - the air there is so polluted on a bad day you can't see 500 metres down the road, and you'd never know if the sun is shining or not. Even flying in a plane at 10,000 metres you're in a grey smog.

No point owning a telescope as it would never be used.

OTOH you could move to Lijiang (2,400m) or Shangri-La (3,500m) where the air really is clean and breathtakingly clear at night.

[hemiorange (Mick)]

yea must agree the night weather here in Melbourne over the last 6 months has been crap. I live up ontop of the dandenongs and its better looking down at the burbs than up at the stars , recently there were two good nights and the second night there was way too much smog to get the scope out and havnt had a good night since !

[OzEclipse (Joe Cali)]

The cross pattern you describe caught my attention. Smog. Haze will cause a halo not a cross.

The cross is most likely to be caused by -
a) spider diffraction
b) Mirror or lens pinched or under tension

Both of the above effects will be smaller, the smaller the light source. So it should be less on the Moon than planets.

The orientation of the cross might tell you something. For example if you have a newtonian and the cross lines up with its 4 spider vanes and has the same orientation as those vanes then that might be the culprit. If it lines up with tensioning screws in an optical cell etc

Joe

[Stonius (Markus)]

Originally Posted by Wavytone

Melbourne ? LOL...

Try some of the big cities in China - the air there is so polluted on a bad day you can't see 500 metres down the road, and you'd never know if the sun is shining or not.

Yes, I worked there on two separate occasions. It was quite oppressive. On some days their pollution was the same as what we would call thick fog. And there were no blue skies. Ever. Their travel brochures are Photoshopped.

They seed the clouds there to make it rain so it strips the pollution from the air. You can hear the shells going off and know it's about to rain like clockwork.

Was such a relief to get home to clear horizons.

[mental4astro (Alexander)]

Hi Ed,

The cross that you mention are diffraction spikes caused by the vanes of the secondary's spider. It can be a symptom of a pinched primary too. Next time you clean your primary you can check the clamps to see that they a bit tight. But in a Newtonian with straight vanes you will get a cross, pinched primary or not.

The haze you see is not uncommon with bright objects. It comes from several sources:
* Light pollutions. A scope will collect not just star light, but ambient light pollution too. The larger the aperture you use in the Big Smoke, the worse the consequences.
* Dirty optics, namely the primary mirror.
* Quality of mirror polish. This introduces more scattering into the image, which appears as haze.
* Internal reflections within eyepieces. The better the quality EP the better the coating qualities to reduce these internal reflections and improve transmission. But also, the more lens elements, the more surfaces there are, and the more inevitable the internal reflections, even ghosting, there can be.

This last point, you can throw money at the problem with expensive EPs. Another options is to use EPs with fewer elements, like orthoscopics, or plossls, the TMB Planetary Type II 'clones', or splash out and get Monocentrics!

Alex.

[AEAJR (Ed)]

Thanks to everyone for your continued advice.

Mirror under tension. Interesting.

Well, it was all clouds tonight again. Even a near full moon doesn't show through.